A Kaiapoi businessman has been convicted and fined $10,000 for animal cruelty, after SPCA officers were forced to euthanase 77 of his sheep.

Dave Clemence, who owns Clemence Drilling, pleaded guilty on Tuesday to charges relating to the ill-treatment of over 112 sheep.

It is the second conviction in 10 months for Clemence, who was found guilty of kidnapping two thieves caught on his property in 2011 and fined $3000 in August last year.

This week he was convicted and fined $10,000, ordered to pay $2040 in veterinary costs, $1000 in solicitors' costs and $130 in court costs for the animal cruelty charges.

Charges were laid by SPCA Canterbury in August last year after inspectors, tipped off by a member of the public, found a number of dead and underweight sheep on his property.

The animals had very little pasture available and supplementary feed provided lacked nutritional value.

Barry Helem, chief executive officer for SPCA Canterbury, said his officers were forced to shoot 77 sheep after veterinary assessments determined their condition was too poor for them to be recovered.

''For them to continue on they would be enduring pain and suffering, so the humane thing was to euthanase.''

He did not know how long the animals had been in that condition.

A further 45 lambs and ewes were recovered and have since been nursed back to health and re-homed.

SPCA Canterbury inspector Clare Ripper said the case had been harrowing for her and her staff.

''Although our aim is to prevent animal cruelty and suffering, the euthanasia of sick and starving animals is extremely distressing for our team, especially when we know their deaths could have been prevented if owners had acted responsibly.''

Helem said the case highlighted the problems that can occur when people are farming part-time.

''All too often we deal with owners who do not understand the responsibilities involved. The two most common problems are failure to provide adequate nutritious feed and failure to seek vet treatment as soon as issues arise.''